Arte de tañer Fantasia

A renaissance treatise on how to improvise fantasias in 3, 4 and more voices. Really interesting treatise, but not easy to use.

For 800 dollars a translation could be yours! :-D
https://www.amazon.com/Art-Playing-Fantasia-Explorations/dp/0935480528

Also great:

start with counterpoint 101 from Earlymusicsources.com
https://www.earlymusicsources.com/youtube/consonances

We have a small quotation from the translation on "How to learn from written music" here:
https://www.thescrollensemble.com/nl/improvisatieles-van-thomas-de-sancta-maria/